Multiple electron gun structure for cathode ray tube



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MULTIPLE ELECTRON GUN STRUCTURE FOR CATHODE RAY TUBE Filed May 31, 1966 3 Sheets-Sheet l 11v VENTOR. GLEN A. BuRDIcK BY gM/ZL/ ATTORNEY 1958 G. A. BURDICK 3,396,297

MULTIPLE ELECTRON GUN STRUCTURE FOR CATHODE RAY TUBE Filed May 31, 1966 5 Sheets-Sheet 2 INVENTOR. GLEN A. BuRD/cK MaZM ,4 T TORNEY 1968 G. A. BURDICK 3,396,297

MULTIPLE ELECTRON GUN STRUCTURE FOR CATHODE RAY TUBE Filed May 31, 1966 5 Sheets-Sheet I5 INVENTOR. GLEN 4. BURDICA ATTORNEY United States Patent 3,396,297 MULTIPLE ELECTRON GUN STRUCTURE FOR CATHODE RAY TUBE Glen A. Burdick, Waterloo, N.Y., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed May 31, 1966, Ser. No. 553,752 5 Claims. (Cl. 313-70) ABSTRACT OF THE DISCLOSURE A cathode ray tube multiple gun structure which comprises a plurality of related unipotential low-voltage focusing lens guns employing overlapping focusing electrodes. In each gun the plurality of successive cylindrical electrodes are axially aligned in sequential order from an end or first electrode having an external alignment diameter. Each successive electrode therefrom has an external maximum diameter which at least equals the maximum external diameter of the preceding electrode. Such structure provides a compact and improved multiple electron gun construction exhibiting enhanced election optics and alignment.

This invention relates to electron discharge devices and more particularly to color cathode ray tube multiple electron gun structures employing unipotential low-voltage focusing lenses.

Many of the cathode ray tubes presently employed in color television display applications are of the type having an envelope with a patterned multiphosphor cathodoluminescent screen disposed on the viewing panel thereof with an apertured structure or foraminous mask positionally spaced therefrom. Electrons from a multiple electron gun mount structure, positioned within the envelope, are beamed through the apertured structure to discretely impinge and luminescently excite the electron-responsive phosphors of the screen. Focusing of the electron beams from the individual guns is usually achieved by means of two cylindrical bipot ntial focus lenses of the familiar equi-diameter type.

The focus voltage of each bipotential gun is commonly in the order of to percent of the anode voltage, thus with an anode voltage in excess of 20,000 volts, the focus voltage may be well above 3,000 volts. It is well known in the art that the proper focusing action of bipotential lenses is critically dependent on the ratio of the focus volt age to the respective anode voltage. To achieve the de sired ratio, it is necessary in color television equipment employing color cathode ray tubes employing bipotential focusing to either regulate the anode voltage to keep it constant or to supply bleeder means for maintaining a sub stantially constant ratio as the beam current changes. Either one of the aforementioned procedures has the re lated manufacturing disadvantage of requiring special circuitry provisions in the allied equipment to accomplish the desired control. From the standpoint of display quality, electron guns employing bipotential focusing tend to bloom or produce large spot size under high beam current condition and are susceptible to degraded focus at the periphery of the screen.

In monochrome cathode ray tubes certain of the aforementioned disadvantages have been overcome by utilizing electron guns having unipotential focusing lenses. An example of this type of gun is the overlapping unipotential, focusing gun wherein a G overlapping focusing electrode is formed to encompass a portion of the adjacent duodiameter G and G electrodes on either side thereof. Since the focusing voltage in this type of gun is normally within the range of 200 to +500 volts it is referred to as employing a low-voltage focusing lens. From the view- 3,396,297 Patented Aug. 6, 1968 point of the manufacturer of television equipment, a cathode ray tube with low voltage focusing is desirable as such voltage is readily and economically available in a typical television receiver.

The assembly of bipotential lens guns into a multiple gun structure is conventionally accomplished by aligning the several electrode elements of each gun on an internally positioned mandrel oriented at the desired angle and extending through the gun elements. With the respective gun electrodes so relatedly positioned, heated insulating rods are simultaneously applied by a beading operation to studding support means projecting from the gun electrodes to integrate the several guns into the mount structure, whereupon, the supporting mandrel is slidably removed from within each aligned gun.

In the overlapping unipotential lens gun, the focusing G electrode has a larger diameter than the adjacent G and G electrodes on either side thereof. Thus, guns of this type cannot be assembled by utilizing withdrawable internal mandrels, as a mandrel which is small enough to go through the G and G electrodes cannot support the larger diametered focusing G electrode.

One type of unipotential lens gun known to the art employs a short focus 6.; electrode which has an inside diameter equal to that of the G and G elements on either side thereof and which does not overlap or encompass these adjacent electrodes. While this short focus lens unipotential gun lends itself to internal mandrel assembly means, it is functionally inferior to the overlapping lens type. In the short focus lens gun it is necessary to use a very short 6., focus electrode, which may be less than 0.125 inch in length, to obtain a focus voltage in the desired region of within .a few hundred volts of cathode voltage. The short G length makes proper alignment of this element with the adjacent elements diflicult to achieve and maintain. In adidtion, the open gaps between the focusing G and the adjacent electrodes subjects the insulating rods to electron charging effect which not only results in distortion of the electron beam being focused but also increases the likelihood of inter-electrode voltage breakdown or arcing.

It is possible to bead the electron guns individually and then assemble the several guns into an integrated mount structure, but this produces an unwieldly and awkward gun structure having a bulk much larger than desired for the current state of the art. In addition, past experi nce has shown that the integration of preassembled guns into a multiple gun structure introduces troublesome alignment problems due to the inherent tolerances present in each of the gun assemblies. Thus, it is extremely difiicult to consistently achieve beam landings of desired quality.

Accordingly, it is an object of the invention to reduce the aforementioned disadvantages and to economically fabricate a compact multiple electron gun mount structure that maintains desired focus over the whole screen under varying beam current conditions.

Another object is the provision of a rigid multiple electron gun structure wherein each low-voltage focusing gun is an assembly of sequentially aligned electrodes in interspaced relationship.

A further object is to provide improved means for fabricating a compact multiple electron gun structure employing overlapping low-voltage focusing lens guns therein.

A still further object is to provide a method for assembling an improved multiple electron gun structure having desired electron optics and alignment.

The foregoing objects are achieved in one aspect of the invention by the provision of a cathode ray tube multiple electron gun structure having therein three unipotential low-voltage focusing lens guns employing overlapping focusing electrodes. The plurality of successive cylindrical electrodes of each gun are axially aligned in sequential order from an end or first electrode having an external maximum alignment diameter. Each successive electrode therefrom has an external maximum alignment diameter which is at least equal to the maximum diameter of the preceding electrode. Fabrication of the unipotential multiple gun structure is facilitated by a plurality of assembly support means having electrode support segments for each gun formed to be compatible with a portion of the external curvature effected by the alignment diameter of each electrode. This provides for each gun a cradle-like aligned arrangement of inter-spaced electrodes each of which has a portion of its cylindrical surface confined within its respective support segment, while another portion of its surface and its studding means are exposed in a sequential longitudinal manner. The loaded support means are relatedly oriented to enable a portion of the exposed cylindrical surface of each electrode to contact a common central support post and be confined thereagainst to facilitate electrode alignment.

The exposed studs are then embedded in heated insulated rods to retain the desired gun alignments. With the removal of the electrode support means and the slidable withdrawal of the common support post, there is provided a compact multiple electron gun structure that exhibits performance and fabrication advantages heretofore unattained.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the accompanying drawings in which:

FIGURE 1 is a plan view of a cathode ray tube;

FIGURE 2 is an enlarged view of the multiple electron gun structure utilized in the tube shown in FIGURE 1 taken along the line 22 of FIGURE 3;

FIGURE 3 is an end view of the multiple electron gun structure taken along the line 3-3 of FIGURE 2;

FIGURE 4 is a view illustrating the assembly means for fabricating the multiple gun structure taken along the line 44 of FIGURE 5;

FIGURE 5 is an end view showing the assembling means of FIGURE 4 taken along the line 5-5 thereof;

FIGURES 6 and 7 are partial plan views of individual electron guns of the multiple gun structure showing the relationship between the G and G electrodes;

FIGURE 8 is an exploded perspective showing the arrangement of the electrode support means;

FIGURE 9 is an elevational view showing an embodiment of the common support post;

FIGURE 10 is a perspective view illustrating another embodiment of the support post;

FIGURE 11 is a longitudinal sectional of the embodiment shown in FIGURE 10 taken along the line 1111 thereof; and

FIGURES 12 and 13 are plan views showing crosssectional embodiments of the common support post.

With reference to the drawings, FIGURE 1 illustrates a typical plural beam shadow mask ty e cathode ray tube 11 having an axis 12 therein. Suitably disposed within the neck portion of the envelope 13 is a multiple gun structure 14 wherein, for example, three electron guns 15 are relatedly positioned approximately 120 degrees apart to provide three electron beams 17. Externally positioned coils 19 are generally utilized to deflect these beams over the raster area and consummate convergence at the apertured structure or shadow mask 21 to pass therethrough and impinge upon the cathodoluminescent screen 23 spaced therebeneath. To facilitate the abovementioned convergence of the separate beams 17 over the entire screen, external dynamic convergence magnets 25 are conventionally employed in conjunction with an internal convergence assembly 27 positioned on the front or screen directed end of the multiple electron gun structure 14. In this specification, the convergence assembl is not considered as part of the multiple gun structure of the invention since it is attached to the unified gun structure subsequent to the fabrication thereof. Therefore, little reference will be made to the convergence assembly herein.

In greater detail, there is illustrated in FIGURE 2 an enlargement of the multiple gun structure 14 in which, to enhance clarity, only two of the three electron guns 15 are shown. These are unipotential, low-voltage focusing lens guns employing overlapping focusing electrodes. structurally, each electron gun comprises an electron source or cathode 29 oriented within a G control electrode 31, a G screen electrode 33, and a G first anode portion arranged substantially in axial alignment to provide the source, control, prefocusing and acceleration for electron beam 17. An electrostatic focusing assembly comprising a G first lens cup 37, a G focusing electrode 39, and a G accelerating electrode having a second lens cup 41 is shown mounted in substantially axial alignment with the aforementioned electrodes upon a plurality of common securement means such as insulating support rods 43. Each of the electrode is suitably supported by studding means 45 embedded in the respective insulating rods to provide the integrated multiple gun mount structure 14.

The relationship of the three electron guns is shown in FIGURES l and 2 wherein the individual guns are positioned about the axis 12' of the unified mount structure. To promote clarity, the subsequently attached convergence assembly 27 is noted in phantom as an undetailed structure.

It will be noted in the embodiment shown, that the successive electrodes comprising each gun, beginning with an end or G electrode thereof, have exterior alignment diameters of discrete cylindrical portions that are equal to or greater than the maximum diameter of the preceding electrode. The substantially cup-shaped G and G electrodes, 31 and 33 respectively, have external maximum alignment diameters 47 and 49 that are substantially equal. The G electrode has an outwardly rolled peripheral edge portion or corona ring 51 having a maximum external diameter 53 greater than the alignment diameter 49 thereof. The G composite electrode 34 has an external alignment diameter 55 which is at least equal to the G corona ring external diameter 53. The first anode portion 35 of the G electrode, having an external diameter 57 smaller than the G alignment diameter 55, is formed for spaced orientation relative to the interior of the G electrode 33. The first lens cup 37 of the multidiameter G electrode is likewise of reduced external diameter 59. Spaced therefrom and in alignment therewith is the duodiameter G electrode 40 having an external alignment diameter 61. The second lens cup portion 41 thereof has an external diameter 63 similar to that of the opposed first lens cup 37.

Formed to coaxially encompass the aforementioned lens cups in a spaced and substantially overlapped relationship, is the cylindrical G focusing electrode 39 having an external alignment diameter 65 which is substantially equal to the external alignment diameters 55 and 61 of the respective adjacent G and G electrodes. To reduce arcing possibilities, the peripheral edges 66 of the G focusing electrode are polished to be free of burrs or projections thereon.

It has been found that an overlapping G electrode having a circumferential dimension or alignment diameter substantially equal to that of the electrodes on either side thereof has several advantages in the multiple gun structure as described herein. First, even though several electron guns are in closely spaced relationship, enhanced shielding is provided to prevent beam distortion in each low-voltage focusing lens. Secondly, improved shielding is also provided in the reverse manner to prevent charging of the insulating support rods which greatly reduces the likelihood of voltage breakdown or arcing; and, thirdly, it has been found that the similar alignment diameters of the aforementioned electrodes in each of the several guns provides an alignment relationship between the guns which promotes the facile integration of the compact multiple gun structure.

With reference to FIGURES 4, 5, and 8, the related assembly of the several guns is shown wherein, beginning with the end or G electrode of each gun, each successive electrode therefrom has an external alignment diameter at least equal to that of the preceding electrode. T o assemble each of the several guns, there is, beginning with the G electrode 31 having the cathode 29 positioned therein, a plurality of integrated external support means 93 in the form of related individual electrode support segments with electrode spacing separators providing longitudinal interspacing therebetween. Each electrode support segment is dimensionally formed according to the respective electrode alignment diameter to be compatible with a portion of the external curvature of the electrode to provide a cradle-like alignment arrangement. Each of the several segments has an aligned aperture 67 therein formed to accommodate an alignment rod 68 which is inserted therethrough to provide an integrated support means for the electrodes of each gun, the several segments and spacers being suitably retained in desired orientation and alignment by afiixing means 69. For example, the G control electrode 31 is loaded into the compatible support segment 71. Successively therefrom, the G screen electrode is positioned in the G support segment 75 being separated from the G electrode by the G G spacer 77. The G G and G electrodes 34, 39, and 40 are seated in the formed G G and G support segments 79, 81, and 83, respectively, with the spacers 85, 87, and 89 therebetween in sequential order with each electrode having a portion of its cylindrical surface alon with its studding exposed in a sequential longitudinal manner.

The several loaded suppont means 93 are then positioned in similar lateral relationship in a suitable seating means such as seating holder 95. Several equispaced holes 97 therein accommodate the lower protruding end of each alignment rod 68 to provide positioning of the aligned electrodes of each gun about a common central support post 99 oriented in the holder. The central support post is equidistantly positioned relative to the aligned electrodes of each gun in a manner so that the exposed cylindrical surface of each electrode of each gun is adjacent thereto.

Securing means for clamping the several positioned support means 93 in an equidistant manner relative to the common central support post 99 is facilitated by utilizing cap 101 having cavities the-rein to receive the ends of the individual alignment rods 68 and central support post 99. Consummation of the clamping step diametrically confines the respective successive electrodes of each gun in spaced longitudinal alignment between the support segments and the central support post. In thi manner, the similar electrodes of each gun are laterally oriented in spaced adjacency with one another.

With all electrodes securely clamped in their respective alignment positions heated insulating support rods 43 are simultaneously applied, by means not shown, to embed therein the plurality of exposed electrode studding means 45. Thus, the electrodes of the several guns are locked into compact aligned confinement.

Release of the clamping means by removing the cap 101 and freeing the alignment rods 68 from the seating holder 95 allows the support segments and spacers of electrode support means to move free from the insulative rod supported electrodes. Removal of the common support post 99 is consummated in a slidable withdrawing manner from between the adjacently oriented end electrodes of the multiple electron gun mount structure.

It will be noted that in the example given, the several electron guns are tilted with reference to the mount structure axis 12. In the tube of this instance, the axis of the mount structure is coincidental with the tube axis 12. The mount structure shown in FIGURES 2, 3, 4, and 5, the assembly of which has been described, has the individual guns angularly tilted toward the tube axis with the terminal or G electrodes being nearest thereto. To achieve this desired tilt, the common support post 99 is in the form of a tapered pin having a center line 100 coincidental with the axis 12 of the mount structure. The external electrode support means for each gun is positioned at a compatible angle in accordance with the taper of the pin thereby maintaining the proper dimensional relationship to facilitate the accommodation of the respective electrodes confined therebetween. Since the G and G electrodes have alignment diameters that are less than those of the successive G G and G electrodes, the common support post 99 has a stepped or dimensionally graduated taper which facilitates both electrode alignment and subsequent post withdrawal; the larger diametrically tapered dimension 103 being adjacent the G and G electrodes of smaller diameter and the smaller diametrical tapered dimension 105 being contiguous with the larger diametered G to G electrodes. With the central common support post or pin having at least one dimensional step therein, transitional to a sequential change in pin cross-sectional dimensions, the larger cross-sectional dimension thereof is adjacent the end electrode to facilitate post-fabrication withdrawal of the pin.

If desired, although not shown, the several electron guns of the integrated mount structure can be tilted away from the tube axis with the G electrodes being nearest thereto. In this instance, in keeping with the teaching of this invention, the terminal or G electrode would be considered as the end electrode with the G G G and G being successive electrodes in reverse order therefrom. Thus, the assembly of the mount structure would be inverted to enable withdrawal of the common support post therefrom upon completion of the fabrication procedure.

It is to be understood that a multiple gun structure having substantially parallel positioning of the guns therein can be fabricated by utilizing a common support post or pin similar to that shown in FIGURE 4 but which has no taper therein.

In FIGURES 6 and 7 other embodiments of the G and G electrode relationship are shown wherein the G screen electrode 33 in FIGURE 6 has an inwardly rolled corona ring 51'. This enables the G alignment diameter 49' to substantially equal the G alignment diameter 55. Similar diametrical relationships are evidenced in FIG- URE 7 where the G electrode has a burr-free edge 32. Thus, the individual electron guns in the multiple structure can be fabricated wherein all of the gun electrodes are of substantially the same external alignment diameters.

Further delineation of the common support post is made with reference to FIGURE 9 wherein the common support means or post 109 has at least one longitudinal support surface 111 that is substantially parallel with the mount structure axis 12 extending substantially axially therethrough. A support post of this type is utilized to assemble the electron guns in parallel relationship. If it is desired to orient one or more guns in parallel or different angular relationships or tilts, with reference to the axis 12' of the mount structure, another embodiment of the common support rod 115 shown in FIGURES 10 and 11 can be utilized wherein at least one portion of the longitudinal surface 117 is substantially parallel with the axis while one or more other portions of the longitudinal surface 119 are angular thereto. The angular relationship of the common support surface to the mount structure axis for all embodiments of the withdrawable post can be referenced from a common intersecting plane 121 perpendicular to the axis 12', wherein the intersection of the plane with the common support surface forms in the direction of support withdrawal at least one exterior having a value not exceeding 90.

In FIGURE 12 another cross-sectional embodiment of the common support post is shown and relates to any portion or portions of the post contacted by electrodes. The substantially triangular embodiment 123 has three longitudinal sides thereon and is oriented in a manner whereby each side thereof provides a surface 124 against which an array of gun electrodes retained by said electrode support means is positioned to consummate gun alignment.

There is shown in FIGURE 13 still another cross-sectional embodiment of the common support means, similarly oriented as that illustrated in FIGURE 12, wherein the pin 125 has three longitudinal flutes 126 formed therein. These flutes are equispaced from the pin center line 100 and from one another with lands 128 therebetween. As previously mentioned, the center lines 100 of the respective pins are coincidental with the mount structure axis 12. Each flute is of an arcuate cross sectional formation 127, so shaped to compatibly accommodate a circumferential portion of the respective electrodes in each gun. The orientation of the pin is such that each flute provides an arcuate contact surface against which a surface portion of each electrode in each gun array, retained by said electrode support means, is positioned to consummate gun alignment.

There is thus provided a compact multiple electron gun mount structure of the low-voltage, overlapping focusing lens variety that is economical to fabricate and wherein each successive electrode has a sequential alignment diameter that is at least equal to the maximum diameter of the preceding electrode. Means for facile assembly are provided wherein the aligned electrodes of the several guns are positioned with external portions adjacent a common support post which is withdrawable from the completed mount structure. The resultant multiple gun structure along with the means and method of assembly thereof are achievements heretofore unattained.

While there has been shown and described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. In a cathode ray tube having an envelope with a cathodoluminescent screen disposed on the viewing panel thereof, an improved multiple electron gun mount structure oriented relative to an axis in said tube to direct electron beams to said screen, said improvement comprising:

at least two overlapping, unipotential, low-voltage focusing lens electron guns mounted relative to one another as a unitary compact structure, each of said guns having a plurality of successive substantially cylindrical electrodes substantially axially aligned in sequential order from an end electrode and spacedly retained by a plurality of insulating rods, at least one of said electrodes having multidiameter portions, one of said electrodes in each gun being an overlapping focusing electrode formed to encompass a smaller dimensioned portion of an adjacent electrode positioned on either side thereof, said end electrode in each of said guns having an external alignment diameter of a discrete cylindrical portion of said electrode with each successive electrode having an external alignment diameter of a cylindrical portion thereof that is at least equal to the maximum diameter of the preceding electrode, said sequential relationship of said diameters facilitates axial alignment of said respective gun electrodes in said compact multiple electron gun mount structure.

2. A cathode ray tube multiple electron gun mount structure according to claim 1 wherein each of said guns comprises an electrode sequence of a G control electrode with an electron source associated therein, a G screen electrode, a G electrode having a first anode portion and a first lens cup, an over-lapping G focusing electrode and a terminal G accelerating electrode having a second lens cup, said end electrode being said G control electrode, said G and G electrodes having substantially equal external alignment diameters with said G having an integrally extending peripherally rolled corona ring of a maximum diameter greater than that of said G alignment diameter, said G G and G electrodes having substantially equal external alignment diameters at least equal to said maximum G electrode diameter.

3. A cathode ray tube multiple electron gun mount structure according to claim 1 wherein said end electrode of each gun is a first grid electrode having an electron source associated therewith, said successive electrodes being positioned in a sequential array from said first grid electrode to a terminal electrode proximal to said screen, said electron guns being tilted toward said tube axis with said terminal electrodes being nearest to said tube axis.

4. A cathode ray tube multiple electron gun mount structure according to claim 1 wherein each of said guns comprises an electrode sequence of a G control electrode with an electron source associated therein, a G screen electrode, a G electrode, an overlapping G focusing electrode, and a terminal G accelerating electrode respectively, said end electrode being said terminal accelerating G electrode with said successive electrodes being in reverse order therefrom.

5. A cathode ray tube according to claim 1 wherein each of said guns has a first grid electrode with an electron source associated therewith, said successive electrodes being positioned in a sequential array from said first grid electrode to a terminal electrode proximal to said screen, said terminal electrode being said end electrode, said electron guns being tilted away from said tube axis with said terminal electrodes being nearest to said tube axis.

References Cited UNITED STATES PATENTS 3,213,311 10/1965 Duerr 3l3-82 3,252,032 5/1966 Kautz et al. 313-82 3,278,779 10/1966 Szegho 3l382 JAMES W. LAWRENCE, Primary Examiner.

V. LAFRANCHI, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION August 6, 1968 Patent No. 3,396,297

Glen A. Burdick It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 74, "exterior having" should read exterior having Signed and sealed this 6th day of January 1970.

(SEAL) Attest:

Eiihrard M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, 

